The present invention relates to wooden blanks and mouldings, and more particularly to mouldings that have substrates covered by a machinable wooden veneer. A reengineered rip saw as described herein preferably is used to form a plurality of lineal mouldings in parallel simultaneously.
The use of mouldings such as base (floorboard skirting), flat and split door jambs, crown (ceiling surrounds), rabbeted jambs (frames), brick mould, and casing (door and window surrounds), are well known. Mouldings generally are decorative, and provide architectural detail. Some mouldings, however, support light loads such as door jambs that support the hinges and doors. It is important that the wood used in the mouldings be of at least a quality corresponding to the type of finish use desired, and the type of load supported. For example, if the mouldings are to be left natural or varnished, then the wood is usually desired to be clear and bright, free of knots, fungus stains, pitch, wood discolerations, glued joints, or other visible blemishes. Such mouldings are known in the construction business as "clear solid grade lineal mouldings," or simply "solid clear mouldings."
Mouldings intended to be covered by paint (or something else that hides the glue joint, color, grain or defect of the wood) are known as paint grade mouldings. The construction industry uses paint grade mouldings in most applications. Using a lower grade knotty or defective or discolored woods, or otherwise imperfect wood, in the fabrication of paint grade mouldings is especially desirable considering that higher quality clear and bright grade woods are generally less plentiful and more expensive. Lower grade woods are less expensive than solid clear mouldings, and the finger joint manufacturing process involved in the fabrication of paint grade mouldings, removes defects that are unpaintable in finished mouldings. The use of paint grade moulding results in a lower cost of the finished moulding applications because long clear bright lengths of natural finished wood are not required. In recent years, the use of clear solid grade mouldings has declined while the use of paint grade mouldings has become more common.
Finger joint moulding is produced using a fifty year old process created to provide paint grade moulding in desired dimensions. Each finger joint moulding is formed by a lengthy multi-step process that includes: 1) ripping strips from a thick plank of wood, 2) cross cutting blocks of paintable and finger-jointable defect-free segments out of each strip by removing those segments having knots, splits, blemishes, or other defects, 3) occasionally reripping the cut blocks strips to a narrower width to remove any broken or wane edges, 4) finger jointing by machining and glueing the resulting accumulated clear blocks to form finger joint blanks of the desired length and dimension, 5) resawing if necessary, with a band saw or rip saw the finger joint blanks in a desired dimension or beveled shape, 6) passing the resulting blank through a multi-headed profiled knife moulder in lineal fashion to form mouldings in their final cross sectional contoured shape, and 7) precision trimming and dado processing the mouldings into the final desired lengths of the moulding. The typical remaining steps for finger joint moulding processing, before shipping, are occasional sanding or patching, priming or painting, and packaging.
Though finger joint moulding is a widely accepted and used paint grade moulding, there are several undesirable characteristics associated with the prior art techniques used to manufacture finger joint mouldings. First, the production of finger joint mouldings is slow, labor intensive, and generates much wood waste. Even with skilled craftsmen and modem machines, approximately 45 to 50 percent cumulatively of the original wood volume used is lost (as sawdust, shavings, and defect blocks) during the many processing stages. The entire board footage volume of finished finger joint moulding profiles fabricated is constituted by an equivilent volume of high quality clear solid wood. The lumber materials used in the fabrication of finger joint moulding are expensive and of limited availability. The finished product being formed from solid bright clear wood is likewise expensive and in limited supply.
Second, each discrete section of wood or blank used in finger joint moulding is composed from multiple smaller blocks or discrete wood sections. Therefore, each discrete wood section is susceptible to its own natural characteristic tendencies of warping, splitting, bowing, cupping, twisting, and other problems common to other discrete lengths of wood. Wood moulding that warps, cracks, or otherwise distorts is difficult and frustrating to work with, and increases scrap. Additional unpredictable waste is generated during the manufacturing process. If the process exposes a defect previously hidden inside the wood and it becomes apparent that a section or block is defective in that manner after it is fabricated into a blank, it can usually result in the entire blank being deemed defective and subject to complete remanufacture to remove such newly apparent defects.
A third undesirable characteristic of prior art finger joint mouldings, shared with other paint grade mouldings and varnish grade mouldings, is that each moulding piece usually has to be moulded separately. Rarely are more than two pieces machined simultaneously in one moulding machine, and two pieces may be machined simultaneously only when the profile has a very small cross sectional dimension as most moulders are not wider than eight inches, and all moulders are not wider than twelve inches. Machining one or two work-pieces at a time (especially when using modern and expensive moulders) is costly in both machine time and labor costs. Such slow, individual, work processing adds to the expense of the moulding significantly and usually results in smaller mouldings being only slightly less costly than mouldings having larger cross sections, or solid clear grade lineal mouldings formed from higher quality wood. Since each moulding piece is moulded separately and since cross cutting is a separate operation, each piece also has to be handled, measured, and cross cut by itself.
Other mouldings are formed as substrates that have veneers covering some or all of their surfaces. Veneers are much more common in furniture component construction than in moulding fabrication. In prior art veneer mouldings, an inexpensive substrate of wood, or other material such as medium density fiberboard, is machined or formed in a quality fashion to the desired shape of the final moulding. A thin strip of veneer (usually cut or sliced from a high quality wood) is then bent or contoured in a shape that conforms directly to the surface of the substrate. The veneer is then adhered to the exposed surfaces of the substrate. If done correctly, veneer mouldings can have an attractive appearance resembling, but being less costly than, solid clear wood mouldings. Veneer moulding is more expensive than finger joint paint grade mouldings. The use of veneer moldings is usually commercially reserved to low volumes of high quality expensive veneer hardwood species where solid wood of that species is difficult or too costly to obtain.
Present veneer mouldings have several shortcomings, however. To form a thin veneer into certain generally commercial standard industry household moulding profiles or desired angles or shapes, the veneer has to be bent sharply to conform to sharply angled contours of the profile. Most veneers are formed from a wood that cannot adapt to very sharp bending, and attempting to bend them sharply causes cracking. Such cracking may occur after the moulding leaves the factory, and perhaps during installation of the moulding. However, most cracking occurs in manufacturing. Sharp angles are therefore not usually found on veneered mouldings. In addition, the adhesive used to attach the veneer to the substrate may fail, allowing the veneer to peel away. The use of veneer mouldings is not very desirable, for most of the large volume of mouldings consumed, because of these cracking and peeling problems. Furthermore, veneer mouldings are still expensive and require a careful machining of the substrate in a linear fashion before the application of the veneer that is also accomplished in a linear fashion. To the trade, veneer mouldings often do not have the appearance of a solid or finger joint wood, and are often equated with either lower valued casegood products or furniture, cabinets, and picture frames. In addition, the costs associated with acquiring veneers and veneering is relatively high.
Another consideration is the machinery that is necessary and used to produce mouldings. Moulding machines are commonly used to shape contoured lineal surfaces of the mouldings. Moulding machines are rarely able to produce a moulding or process a blank that is a foot wide or wider. The moulding machines are relied upon largely because they can provide cuts having extremely close tolerances and/or complex curves. If mouldings are milled by machines that do not operate within these tolerances, then certain ones of the edges of the work piece may be misshaped, the exposed wood of the mouldings may have raised or torn grains, or the lineal surfaces may have washboard surface effects. Further machining, or occasionally sanding, is necessary to smooth the surfaces of work pieces having such washboard surfaces. Many times it is simply impossible to repair the surface and the entire product must be scrapped. Other prior art machines usually do not produce mouldings that are as attractive as mouldings produced by moulding machines. Moulding machines require complex engineering and tooling. The moulding machines are individually built by hand and require precise tolerances in the machine and tool steel used. Therefore, they are relatively expensive to purchase. Operating moulding machines requires a high degree of skill and the maintenance is expensive and technically burdensome.
Another type of machine used in the process of fabrication of mouldings are planer or matchers. These are primarily used to plane or smooth the outer surface of lumber or a blank in a lineal manner. It is impossible to cut through a piece of wood to form multiple separate lineal mouldings from a single piece of wood using a planar. Planers are less expensive to buy and operate than moulders that have similar board footage throughput capabilities, but can only perform a limited function.
Rip saws are also used in moulding fabrication to provide cuts that extend lineally through pieces of wood. Rip saw cuts do not have to generate much wood waste. However, forming curved or contoured lineal surfaces using rip saws is not possible. From these foregoing paragraphs, it should be evident that each of the moulders, planers, and rip saws have their own purpose in moulding fabrication. Not only does each prior art piece of machinery work on very few pieces at any one time (in a lineal fashion). Additionally, to form many mouldings, there are multiple necessary processing steps that often require different machines.
In a certain prior art system, where work pieces that have edge-glued panels or lamenated substrate panels machined into a panel or moulding having finished contoured edges or surfaces, the product is produced by machining, using routers as cutting tools which move about the work piece while maintaining the work piece in that fixed location. An example of a machine that cuts in this manner is a computerized numerical control routing machine. Such routers are usually limited to a maximum of four or five routing heads working simultaneously on one work piece. Such computerized numerical control systems are complex to program, expensive to purchase, and typically machine large surface areas relatively slowly. They are not a practical alternative to moulding machines.
The greatest volumes of mouldings sold are standardized profile shapes and sizes that have a simple but well defined contoured cross section. These rectangular cross sectional rounded edges and simple "S" edges and radius curved cross sectional mouldings represent approximately 85 percent of the mouldings sold. Intricately curved and angled cross sectional mouldings and very complex profiles traditionally represent approximately 15 percent of moulding volume. Many prior art machines used to produce mouldings therefore are more complex, and can provide profiles of much greater intricate architectural detail and variations in design, than is necessary for the predominant volume of mouldings made and consumed by the housing and commercial construction industry.
Reducing the costs of machinery, labor, and the bulk of the raw material consumed in moulding production, and yet providing a technique for producing mouldings formed from multiple wood sections with a high quality appearance, is highly desirable. Limiting the percentage of high quality wood contained within such mouldings, and the waste associated with producing such mouldings, is also desirable. Replacing such high quality woods with lower quality woods, wood substitutes, or other materials is desirable where such replacement does not detract from the appearance sought or the properties necessary for use of the mouldings. Production of a veneered moulding that appears as if it were solid wood and permits the machining of sharp cross sectional curves and angles on the contoured profile is also desirable. It is desirable to make it difficult to distinguish a veneered mouldings from other conventional solid wood mouldings based upon surface appearance alone. It is desirable to provide a machine that is not extremely complex to operate and maintain and of lower cost to buy than a conventional moulder which can inexpensively mill the wood into high quality mouldings with close cross sectional tolerances and do so in volume. It is also desirable to provide a machine that can profile multiple lineal mouldings simultaneously at regular moulder feed speeds. The present invention satisfies these desired features using relatively uncomplicated technology.